1. Field of the Invention
The present invention relates to an ink jet printer head actuator and a manufacturing method thereof, and more particularly, the present invention relates to an ink jet printer head actuator and a manufacturing method thereof, in which a protective thin film serving as an etching ceasing layer is integrally deposited between a vibrating plate and a chamber plate made of thin metal plates, whereby formation of a plurality of chambers by etching in the chamber plate is performed in a more precise and economical manner, and the vibrating plate is prevented from being corroded due to direct contact with ink, whereby mechanical rigidity of a printer head is improved.
2. Description of the Related Art
Generally, ink firing scheme in an ink jet printer head is largely divided into a thermal bubble jet type ink firing scheme and a piezo transducer type ink firing scheme.
In the thermal bubble jet type ink firing scheme, by electrically heating a chamber, ink which is stored in a chamber is fired through a nozzle by thermal expansion. In the piezo transducer type ink firing scheme, by driving a vibrating plate by a piezoelectric actuator, ink which is stored in a chamber is fired through a nozzle by vibrating force of the vibrating plate.
Because ink particles fired in these manners as described above have a size of several tens .mu.m (about 40 .mu.m) and a plurality of particles are fired simultaneously in many places, precise operability is required above all things.
FIG. 1 illustrates an embodiment of the piezo transducer type ink firing scheme which is widely used between the two ink firing schemes. In the piezo transducer type ink firing scheme, as a piezoelectric device, PZT is used.
In an ink jet printer head used in this piezo transducer type ink firing scheme, a nozzle plate 110, a reservoir plate 120, a restrictor plate 130, a chamber plate 140 and a vibrating plate 150 are sequentially laminated from bottom to top. A lower electrode 161, a piezoelectric element 163 and an upper electrode 162 are also sequentially laminated on the vibrating plate 150 thereby to constitute a piezoelectric actuator 160.
In the above construction, the nozzle plate 110 is formed at its one side with a nozzle 111 of a small diameter. The nozzle 111 defines a discharging hole through which ink is actually fired.
The reservoir plate 120 which is laminated on the nozzle plate 110 is formed at one side thereof with a through hole 122 which is communicated with the nozzle 111 of the nozzle plate 110 for introducing ink into the nozzle 111 and at the other side thereof with a reservoir 121 which stores a proper amount of ink.
The restrictor plate 130 which is laminated on the reservoir plate 120 is formed at one side thereof with a through hole 132 which is communicated with the through hole 122 which is formed in the reservoir plate 120 to define a fluid passage and at the other side thereof with a restrictor 131 of a small diameter such that the restrictor 131 is communicated with the reservoir 121 for allowing a predetermined amount of ink to flow therethrough.
The chamber plate 140 which is laminated on the restrictor plate 130 is formed with a chamber 141 which are simultaneously communicated with the restrictor 131 and the through hole 132 which are formed at both sides of the restrictor plate 130, respectively. Ink flows into the chamber 141 through the restrictor 131 and flows out of the chamber 141 through the through hole 132. The chamber plate 140 allows ink flowing out of the chamber 141 to be fired through the nozzle 111 of the nozzle plate 110 after flowing through the through hole 132 of the restrictor plate 130 and the through hole 122 of the reservoir plate 120.
On the other hand, the vibrating plate 150 which is laminated on the chamber plate 140 covers an upper end of the chamber 141 which is opened at an upper end of the chamber plate 140. The vibrating plate 150 enables ink flowed into the chamber 141 to flow out of the chamber 141 through the through hole 132 of the restrictor plate 130. In this connection, the vibrating plate 150 serves as an operating section which actually changes volume of the chamber 141 by its flexural deformation, thereby changing pressure in the chamber 141 to allow ink to flow.
Because the flexural deformation of the vibrating plate 150 cannot be naturally generated, the piezoelectric actuator 160 is provided on the vibrating plate 150 for rendering the flexural deformation of the vibrating plate 150.
As described above, the piezoelectric actuator 160 comprises the lower electrode 161, the upper electrode 162 and the piezoelectric element 163 intervened therebetween. The piezoelectric actuator 160 serves as driving means which generates deformation of the piezoelectric element 163 by intermittent control of electric power which is supplied from the outside to the piezoelectric element 163.
In other words, piezoelectric element 163 contracts and expands depending upon electric power supply between the upper electrode 162 and the lower electrode 161, and as this flexural deformation of the piezoelectric element 163 is transferred to the vibrating plate 150 as it is, the flexural deformation of the vibrating plate 150 is generated.
Accordingly, if the piezoelectric actuator 160 is electrically driven, as the flexural deformation of the vibrating plate 150 is generated, the volume within the chamber 141 of the chamber plate 140 is changed. If the volume expands, ink flows into the chamber 141 from the reservoir 121 through the restrictor 131, and if the volume contracts, ink flows out of the chamber 141 through the respective through holes 132 and 122 and the nozzle 111 of the nozzle plate 110.
On the other hand, as the conventional piezoelectric element is required to endure a high temperature (conventionally 800.degree. C.-1200.degree. C.) due to its manufactural peculiarity, the lower electrode 161 and the vibrating plate 150 which are provided below the piezoelectric element 163 must be made using heat resistant material (such as platinum, zirconium, etc.) which will not be deformed at a temperature higher than the above temperature. However, recently, as a method for manufacturing a piezoelectric element at a low temperature is disclosed in the art, it is possible to use various materials for making the vibrating plate 150.
However, because the vibrating plate 150 is flexurally deformed as actual operating means which functions to suck ink into the chamber 141 and discharge ink through the nozzle 111, there is caused a problem in that adherence between the vibrating plate 150 and the chamber plate 140 is likely to be deteriorated.
That is to say, in order to couple the chamber plate 140 to the vibrating plate 150, in the conventional structure in which the vibrating plate 150 and the chamber plate 140 are made of ceramic materials, the vibrating plate 150 in the form of paste is applied onto the manufactured chamber plate 140 and then baked. Also, alternatively, separately manufactured vibrating plate 150 and the chamber plate 140 can be bonded to each other by using adhesive.
Especially, as shown in FIG. 2, the coupling structure between the vibrating plate 150 and the chamber plate 140 can be obtained in such a manner that a non-metallic mold 200 is attached to the vibrating plate 150 to define a space which is to be the chamber 141, and after the chamber plate 140 is formed around the non-metallic mold 200 by electroforming, the non-metallic mold 200 is removed.
However, with this methods for coupling the vibrating plate 150 and the chamber plate 140 with each other by baking or bonding as described above, not only it is difficult to maintain sufficient mechanical rigidity between the vibrating plate 150 and the chamber plate 140 when the vibrating plate 150 is flexurally deformed, but also it is difficult to form the plurality of chambers 141 having a size of several hundred .mu.m (about 200 .mu.m) in the chamber plate 140 such that they have an interval (about 100 .mu.m) between two adjoining chambers 141, which is less than the size of themselves. Specifically, since separate costly equipment is required in order to form the plurality of chambers 141, manufacturing cost of the printer head is increased.
Also, in the case that the plurality of chambers 141 are formed by electroforming as shown in FIG. 2, as a fine difference is induced depending upon particulars in attaching the non-metallic mold 200 to the vibrating plate 150, as can be readily seen from FIG. 3, it is difficult to keep constant a distance t1 from an outside edge of the chamber plate 140 to the chamber 141 and an interval t2 between two adjoining chambers 141. Especially, since there is a tendency that the distance t1 from the outside edge portion of the chamber plate 140 to the chamber 141 is larger than the interval t2 between two adjoining chambers 141, adhering strength between the chamber plate 140 and the restrictor plate 130 varies from article to article.